饲料维生素C含量对圆斑星鲽幼鱼抗氨氮胁迫能力的影响

摘要

氨氮污染是水产养殖中重要的污染物，因此提高鱼体抗污染应激能力至关重要。本试验采用不同维生素C含量的饲料饲喂圆斑星鲽幼鱼，探究饲料维生素C含量对圆斑星鲽幼鱼抗氨氮胁迫能力的影响。试验在（12．5±1．5）℃的水温下进行，选择体重为（38．0±0．8） g的健康圆斑星鲽幼鱼，随机分为7组（每组3个重复，每个重复30尾），分别投喂维生素C含量为10．2（对照）、249．1、402．8、616．2、769．5、909．4和1177．8 mg／kg的试验饲料8周。投喂试验结束后，从每个重复取10尾鱼，用20 mg／L的氨氮胁迫24 h。结果表明：无论是氨氮胁迫前还是氨氮胁迫后，在饲料维生素C含量达到769．5 mg／kg时，肝脏和肌肉中维生素C积累达到饱和，再继续升高饲料维生素C含量，肝脏、肌肉中维生素C含量不再显著升高（ P＞0．05）。除1177．8 mg／kg维生素C组外，无论是氨氮胁迫前还是氨氮胁迫后，各维生素C添加组圆斑星鲽幼鱼血清中过氧化氢酶（CAT）和超氧化物歧化酶（SOD）活性均显著高于对照组（P＜0．05）。除616．2 mg／kg维生素C组血清中CAT活性无显著变化（ P＞0．05）外，氨氮胁迫使各组血清中CAT和SOD活性显著降低（ P＜0．05），但添加维生素C可以减少降低的幅度。无论是氨氮胁迫前还是氨氮胁迫后，各维生素C添加组鳃丝Na＋／K＋⁃ATP酶活性均显著高于对照组（ P＜0．05）。氨氮胁迫使对照组及909．4和1177．8 mg／kg维生素C组鳃丝Na＋／K＋⁃ATP酶活性显著降低（P＜0．05），其他组则无显著变化（P＞0．05）。氨氮胁迫使各组血清中葡萄糖和乳酸含量显著升高（P＜0．05），对照组血清中皮质醇含量显著升高（ P＜0．05）。此外，氨氮胁迫使各组血清中总铁结合力显著降低（P＜0．05）。综合各项测定指标，圆斑星鲽幼鱼饲料中维生素C含量在402．8～616．2 mg／kg时可有效提高机体抗氨氮胁迫能力。%Ammonia⁃nitrogen pollution is one of the important pollutants in aquaculture, thus improving the re⁃sistance of pollution stress of the fish is very important. This experiment using different vitamin C content diets to feed juvenile spotted halibut ( Verasper variegatus) , in order to get the effects of dietary vitamin C content on anti⁃ammonia⁃nitrogen stress ability of juvenile spotted halibut. Water temperature was maintained at (12.5± 1.5) ℃ in this experiment. Juvenile spotted halibut with the body weight of (38.0±0.8) g were randomly as⁃signed into 7 groups with 3 replicates per group and 30 fish per replicate, and fed 7 experimental diets with the vitamin C content was 10.2, 249.1, 402.8, 616.2, 769.5, 909.4 and 1 177.8 mg/kg, respectively. The ex⁃periment lasted for 8 weeks. After feeding trial, each replicate selected 10 fish to stress 24 h by 20 mg/L am⁃monia⁃nitrogen. The results showed as follows: whether before or after ammonia⁃nitrite stress, the vitamin C accumulation in muscle and liver reached saturation when dietary vitamin C content was 769. 5 mg/kg, and continued to rise the dietary vitamin C content, the vitamin C content in muscle and liver was not significantly increased ( P>0.05) . The activities of serum catalase ( CAT) and superoxide dismutase ( SOD) in vitamin C addition groups except 1 177. 8 mg/kg vitamin C group were significantly higher than those in control group whether before or after ammonia⁃nitrite stress ( P<0.05) . The activities of serum CAT and SOD in groups ex⁃cept serum CAT activity in 616. 2 mg/kg vitamin C group were significantly decreased by ammonia⁃nitrite stress ( P<0.05) , and decline ranges in vitamin C addition groups were less compared with control group. The gill Na+/K+⁃ATPase activity in vitamin C addition groups was significantly higher than that in control group whether before or after ammonia⁃nitrite stress (P<0.05). The gill Na+/K+⁃ATPase activity in control group and 909.4, 1 177.8 mg/kg vitamin C groups was significantly decreased ( P<0.05) , but that in other groups had no significant change after ammonia⁃nitrite stress ( P>0.05) . Ammonia⁃nitrite stress significantly increased the contents of serum glucose and lactic acid in all groups (P<0.05), and significantly increased the serum cortisol content in control group ( P<0.05) , while significantly decreased the serum total iron binding capacity (TIBC) in all groups (P<0.05). Base on a comprehensive consideration of various measured indices, when dietary vitamin C content is 402.8 to 616.2 mg/kg, the anti⁃ammonia⁃nitrogen stress ability of juvenile spotted halibut can be effectively improved.